POC has oversight of CORE; PAB advises POC; therefore the oversight 
is transitive.  Here's a concrete (but hypothetical) example:  POC 
has recieved much input from the community that certain activities on the 
part of certain registrars should be considered unethical.  POC asks 
PAB for advice; PAB recommends that policies be changed; as a result 
of these policy changes some registrars go out of business.
And I refer you to section 4b of the CORE MoU:
    As provided in Section 6(j)(ii), (iii) and (v) of the gTLD-MoU,
    the POC may from time to time establish new terms and conditions
    for applications by entities desiring to be Registrars, and may,
    following consultation with the PAB and CORE, remove Registrars
    who do not operate consistently with the requirements of the
    gTLD-MoU and the CORE-MoU.  Until such time as the POC provides
    otherwise, the provisions of this Article shall apply to all
    applications. 
-- Kent Crispin "No reason to get excited", kent@songbird.com the thief he kindly spoke... PGP fingerprint: B1 8B 72 ED 55 21 5E 44 61 F4 58 0F 72 10 65 55 http://songbird.com/kent/pgp_key.html